Directly heated pulp digester



y 26, 1931- E. MORTERUD' 1,807,544

DIRECTLY HEATED PULP DIGESTER Filed Feb. 26. 1929 f/i YEA fa? W Patented May 26, 1931 PATENT OFFICE EINAR MORTERI TD, OF TORDEROD, NEAR MOSS, NORWAY DIRECTLY HEATED PULP DIGESTEB Application filed February 26, 1929. Serial No. 342,742.

The present invention relates to digesters for wood pulp and the like adapted to be heated by direct introduction of steam into the digester.

In digesters of this. type it has been customary to inject steam at or near the bottom of the digester, whereby the liquor is caused to circulate in the digester on the thermosiphon principle.

As it is desired to heat the whole contents of the digester as quickly as possible, it is necessary that a rapid circulation of the liquor should take place, andthis, in accord- .ance with the above mentioned system of 5 heating, is directly dependent on the difference in temperature existing in the" various parts of the digester.

In a pulp digester, the contents of which are to be heated as evenly as possible in order to perform certain chemical reactions, it is however on the other hand not desired to establish considerable temperature differences. and accordingly an advantage obtained with regard to rapid heating in digesters of the as kind referred to will always be accompanied by a drawback with regard to uneven temperature.

In accordance with the present invention direct heating of pulp digesters takes place by means of steam injected into the digester through a number of openings located in the middle or cylindrical part of the digester.

The steam inlet openings in accordance with the present invention may be distributed as along a substantial part of the digester, or they may be located in the same level at or near the central part of the digester.

In both cases it is preferred to provide the digester with mechanical means for circulat- 60 mg the liquor in such a manner that a con-,

tinuous unidirectional current of liquor passes through the whole of the digester, the

current in the opposite direction being conducted through a tube or conduit inside or outside the digester by means of a pump or the like.

Although it is preferred as stated above to provide the digester with such mechanical circulating means, the system of heating in 5 accordance with the present invention may also be adopted independent of such mechanical circulating means.

On the drawings Fig. 1 is a longitudinal section of a pulp digester in accordance with one embodiment of the invention.

Fig. 2 is a longitudinal section through a pulp digcster in accordance with a second embodiment of the invention.

In the embodiment illustrated on Fig. 1, 1 is the digester. A pump 3 serves to convey liquor from the bottom of the digester through circulation pipe i with intake sieve 2 to outlet openings 6 near the top of the digester. Y

Inlet openings 5 for heating steam are distributed over a substantial part of the middle or cylindrical part of the digester. As it will be noted these openings are located at different levels, and the openings of different levels are angularly displaced with regard to each other with the object that the steam injected through one opening shall have ample time to condense completely 1n the liquor before reaching another steam H inlet.

fAs seen on the lower lefthand side of Fig.- 1 each steam inlet 5 may be covered by a sloping screen 7, which may preferably be perforated in order to keep the pulp away but let the liquor pass. I

In this manner it is obtained that the steam upon entering comes in immediate contact with a considerable volume of liquor without striking the stationary pulp fibers.

Also it is an advantage of the sloping defleeting screens 7 that they serve to atomize the steam and to deflect the steam bubbles in a downward direction.

In accordance with the embodiment illustrated on Fig. 2 the steam inlet openings are placed in annular steam distributing pipes 8, 9, one of which follows the interior wall of the digester, whereas the other one has a smaller diameter and is located at a different level.

Both annularsteam inlet pipes are protected by deflecting screens 7 for the purpose described in connection withFig. 1, the deflecting screen 7 for the annular distributing pipe 9 having a roof-shaped cross section and being supported from the wall of the digester by means of stays 10.

Although two annular distributing pipes 8 and 9 are illustrated on Fig. 2 it may be sufiicient to use only one distributing pipe, and also it may in some cases be desirable to locate two or more annular pipes at the same level instead of at different levels as illustrated on Fig. 2.

10 Claim:

In a directly heated pulp digester the combination with a plurality of steam inlet openings in the middle or cylindrical part of the digester of mechanical means for causm ing the digester liquor to circulate in an unidirectional current through the digester.

In testimony whereof I affix my signature.

EINAR MORTERUD. 

